THE SURVIVAL OF 1612-MHZ OH MASERS IN ASYMPTOTIC GIANT BRANCH PLUS WHITE-DWARF BINARIES.
MON NOT R ASTRON SOC
1017 - 1024.
We have constructed a model of the OH distribution in an oxygen-rich outflow from an asymptotic giant branch star possessing a white dwarf companion. We assess the probability of 1612-MHz OH maser emission occurring despite the presence of a luminous accretion disc around the white dwarf. We find that the OH is resistant to photodissociation in all but the least massive winds, as a result of shielding by the dust component of the AGB outflow and self-shielding by H2O and OH molecules. This conclusion only partially supports the suggestion of Lewis that a similar to 40 per cent nondetection rate of OH 1612-MHz masers in potential OH/IR stars is due to photodissociation of OH. Our results are more compatible with the more tightly directed survey by Lewis and Engels of oxygen-rich OH/IR-star colour 'mimics', which shows a 1612-MHz detection rate of at least 75 per cent. We also postulate that other effects, such as the disruption of the velocity coherence of the wind, may be as important as photodissociation in inhibiting maser formation in AGB + WD binary systems.
|Title:||THE SURVIVAL OF 1612-MHZ OH MASERS IN ASYMPTOTIC GIANT BRANCH PLUS WHITE-DWARF BINARIES|
|Keywords:||MASERS, STARS, AGB AND POST-AGB, BINARIES, GENERAL, CIRCUMSTELLAR MATTER, STARS, MASS-LOSS, RADIO LINES, STARS, INTERSTELLAR RADIATION-FIELD, STAR COLOR MIMICS, CIRCUMSTELLAR ENVELOPES, PHOTODISSOCIATION RATES, IR STARS|
|UCL classification:||UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Physics and Astronomy|
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